This invention relates to an engine control and more particularly to an improved engine knock control for a direct injected, internal combustion engine.
In spite of the advantages of two cycle engines over four cycle engines in regard to complexity and high specific output, the environmental concerns are causing reappraisal of the continued use of two cycle engines. Specifically, the overlap between the scavenge port and exhaust port opening and closing gives rise to the possibility that unburned hydrocarbons may pass into the atmosphere through the exhaust port.
It has been thought that the performance of these engines can be improved by utilizing such methodologies as feedback control and/or direct cylinder fuel injection in order to improve their performance and make their continued use more feasible.
With feedback control systems, an engine combustion condition sensor such as an oxygen sensor is positioned in proximity to the combustion chamber or the exhaust system so as to sense the oxygen content of the exhaust gases at the completion of the burning cycle. By determining the amount of oxygen present, it is possible to tell if the engine is running rich or lean. Then, feedback control is possible to maintain the desired fuel/air ratio and, accordingly, improve the exhaust emission control.
Direct cylinder injection also is useful in improving engine performance. With direct cylinder injection, the amount of fuel injected per cycle can be more accurately controlled and this is particularly important with two cycle engines.
However, when two-cycle engines employ fuel injection and the fuel is injected directly into the combustion chamber, the risk of having the fuel pass out of the exhaust port is substantially increased. Therefore, there has been proposed in our copending application entitled "Control for Direct Injected Two-Cycle Engine," Ser. No. 09/188,953, filed Nov. 10, 1998, and assigned to the Assignee hereof, an injection system wherein the timing of fuel injection is controlled so as to be more advanced from the prior art methods so that it occurs before the exhaust port has been totally closed.
The injection timing is initiated, however, at a time so that the first injected fuel will not reach the exhaust port before it closes. This system provides a significantly improved engine performance and emission control.
The system described in our aforenoted copending application provides very good basic engine control for the engine and particularly for a direct injected engine having feedback control. However, there are some conditions when other types of control may be desirable to improve engine performance.
For example, there may be a condition arise which is commonly referred to as "knocking." Actually, knocking can result under two different types of running conditions. One of these is during an extreme acceleration and the other is when operating at a steady state condition but wherein the load on the engine may change and require some form of knock control.
If feedback control is utilized when these conditions arise, then the knock control must be done by a means such as adjusting engine timing or some other expedient, which may not always be the most effective or the most desirable.
It is, therefore, a principal object of this invention to provide an improved fuel injection control from an internal combustion engine having direct cylinder injection that incorporates manipulation of the fuel injection control so as to provide knock control.
It is a further object of this invention to provide an improved knock system and arrangement for a direct injected internal combustion engine.
As has been noted, engine knocking can arise under some different circumstances. It has been discovered in connection with this invention that the type of fuel injection control in order to improve knock under these running conditions may be different.
It is, therefore, a still further object of this invention to provide an improved fuel injection control for an internal combustion engine wherein the type of fuel injection control applied depends upon the running condition under which the knocking occurs.